Electrodeposition



March 5, 1957 P. J. TOPELIAN 2,784,151

ELECTRODEPOSITION Filed March 25, 1955 INVENTOR. PAUL J.TOPELIA N ATTOR NEY United States Patent ELECTRODEPOSITION Paul J. Topelian, Newark, N. J., assignor to Tiarco Corporation, Newark, N. J., a corporation of New Jersey Application March 25, 1955, Serial No. 496,750 19 Claims. (Cl. 204-23) The invention relates to improvements in electrodeposition, and more particularly to methods for distributing current and the distribution of metal deposited in plating of articles of irregular shape, or articles having multiplanar areas.

Plating baths which have poor throwing power, or baths requiring the use of relatively high current densities, present coverage problems when the object to be plated is of irregular shape. Those portions of the article located closer to the anode receive a heavier deposit than the portions which are farther away. Objects which are quite regular in shape, but which have an edge or corner where two or more surfaces meet also present difliculties when it is desired to plate the edge or corner. Treeing or excessive rounding occurs at the edge of the multi-planar area.

Various means have been used to overcome the afore mentioned problems. These previously known means possess individual limitations of one kind or another. A common device for obtaining more uniform current distribution and metal deposit coverage is the shaped anode. Shaped anodes, however, can only be used where the object to be plated is not unduly complicated in shape. Otherwise, the cost of making a conforming anode becomes prohibitive. Moreover, a shaped anode is onlyuseful for plating an article of given contour, and, therefore, affords little of the flexibility desired in a plant handling a wide variety of articles of many diiferent shapes.

Thieves or robbers have been widely used to obtain improved current distribution or coverage. These auxiliary conductors are placed near points of abnormally high current density to divert current away from such points. Such conductors must be carefully spaced from the selected points or areas of the object. Such spacing is critical, timeand effort-consuming, and economically burdensome. Moreover, there are someobjects having such irregular shapes that the use of a thief is imprac- I l tical, if not impossible.

Shields or masks, which are made of non-conductive material, have been .used to divert current away from areas where it concentrates unduly. This approach has only limited application, because many irregularly shaped articles require continuous coverage, ratherthan selective coverage and non-coverage.

It has also been proposed to provide a supporting cathode fixture formed with a serrated edge to engage the edge of a metal sheet to be plated. This fixture supports a fiat sheet in the bath, the cathode current being supplied to the supporting fixture. The edge of the sheet engaged by the serrated edge of the supporting fixture was found to be uniformly plated, notwithstanding direct contact with the serrated edge. This prior art device has limited application, there being many objects which have contours which would not permit its use. 7

I have found that by covering the multi-plauar area 'of an object, whether projections and recesses of an irregu- 2,784,151 Patented Mar. 5,1957

shaped object, with a flexible, porous, electrically-conductive sheet or fabric, over-all metal deposition is obtained, while preventing treeing or undue rounding of the objects projections or edges. While any deformable, foraminous, electrically-conductive sheet may be used, I prefer to use ordinary, commercial, woven wire-meshfabric or screening. Being deformable, it can be wrapped around the object, assumes and retains the shape given to it upon bending, and thereby permits the object itself to serve as its support. .Instead of expensive forming operations to make a shaped anode for. a given article, or requiring great care in critically spacing a thief from a projection, the current distributing means of the present invention is applicable to an extremely wide variety of objects having different multi-planar areas in a very simple, inexpensive and universal manner.

In accordance with the present invention, objects of such widely different shape and contour as twist drills, countersink bits, reamers, taps, saws, knives, cutters, gears, variously shapedpunches and'dies; in fact, practically any object having a multi-planar area, may be plated in baths possessing poor throwing power, or baths requiring high current densities, withthe accomplishment of sharp defined plated project-ions or edges and deposition within the recesses. In the case of cutting tools, the metal deposited conforms tof the cutting edge so well that subsequent sharpening is often not needed. It will thus be apparent that the present invention possesses great advantages in industrial chromium plating. Tools, punches and dies of high carbon steels or of tungsten carbide have their life increased several-fold. The chromium plated objects have imparted to them the advantageous properties of chromium, such as a low coefiicient friction, resistance against spalling, extreme hardness and resistance to corrosion. 1

Other objects, advantages and results of the invention will be brought out by the following description in conjunction with the accompanying drawings, in which:

Fig. 1 is a plan view of a wire-mesh fabric, which preferably is used to carry out the present invention;

Fig. 2 is a 'plan view of a twistdrill being'prepared' Fig. 4 is an enlarged transverse vertical sectional viewtaken approximately in the plane of line 4-4 of Fig. 4;

Fig. 5 is a cross-sectional view of a plating bath showing the prepared twist drill being plated;

Fig. 6 is a side elevational view of a saw having its cutting edges covered withthe current distributing means of the present invention preparatory to insertion in a plating bath;. I

Fig. '7 is an enlarged, transverse vertical sectional view taken approximately in the plane of line 7-7 of Fig. 6; and

Fig. 8 is a perspective view of a spur gear having its teeth covered with the current distributing means of the present invention.

The method of the present invention, and the novel results obtainable from the practice thereof, may generally be described in connection with the chromium plating of high-speed twist drills.- A one-quarter inch highspeed twist drill A is'first degr'eased in a manner wellknown in the art, and then covered with a deformable, porous, electrically-conductive sheet orfabric B. Preferably, the sheet. or fabric B comprises woven wire-mesh fabric of the ordinary commercial type, such as a onesixteenth inch mesh screening, from which the galvanized coating has been removed. The wire-mesh fabric may be made of any other suitable metal, such as, copper or brass. Also, instead of a wire-mesh fabric, the deformable, porous, electrically-conductive sheet may be made by suitably perforating a thin metal sheet.

As shown in Figs. 2 to 4, to cover the drill A, a strip of wire-mesh fabric B is used having a width equal to, or very slightly greater than, the circumference of the drill. The length of the strip is made approximately three-quarters of an inch longer than the drill body 10 so that the strip extends beyond the drills lips or cutting edges 12 and for a short distance up on the shank 14. The strip B is tightly wrapped or bent around the body of the drill, thereby forming a longitudinal seam 16 where the longitudinal edges of the strip abut each other. The strip is pinched at the lower end 18 so that the strands do not touch the cutting edges'lz, although care need not be exercised to avoid the contact. In any event, the mesh fabrictightly envelops the body of the drill so that the wire-mesh fabric covers and is against the land portion 20 of the drill. No efiort is made to force the wire-fabric into the drills flutes 22. The drill is then masked at the top or shank 14, as by lacquering or by Wrapping a strip of insulating material 24 around it with a hooked strap member 26 therebetween. The wire-mesh covered drill is then anodically cleaned, rinsed, dipped in muriatic acid, and rinsed in accordance with wellknown cleaning practices. The thus prepared object is then hung from the cathode bar 28 of a chromium plating bath 3t) and surrounded by equi-distantly spaced anodes 32. V i I The chromium plating bath may be of any known industrialor engineering type. Specifically, a bath containing thirty-two ounces per gallon of chromic acid and 0.32 ounce per gallon of sulphate in the form of sulphuric acid was used. The bathwas maintained at a temperature of 120 to 125 F. and plating carried out with a current density of 3 amperes per square inch. For comparative purposes, a twist drill degreased and cleaned in the same manner, but without the wire-mesh fabric lB thereon, was also placed in the chromium plating bath.

After three (3) minutes, both drills were removed from the tank. The drill without the mesh-fabric was found to have treed? on the cutting edges 12 and on the helical edge, designated 34, where the land and the flute of the drill meet. The drill covered with the wire mesh fabric, upon removal of the covering fabric, did not show any treeing whatever on either the cutting edges 12 or the edge 34. The cutting edges 12 and the edge 34 were covered with chromium, with the initially sharp edges just as sharply defined. Some chromium deposit appeared near the top of the flute.

Additional drills were prepared as hereinbefore described and placed in the chromium plating bath under the described temperature and current density conditions for periods of five ten fifteen thirty forty-five sixty seventy-five ninety one hundred and five one hundred and twenty and one hundred and fifty minutes. After ten minutes in the tank, the flutes, as well as the land and edges 12 and 34 were completely covered with chromium, and the edges 12 and 34 were sharply defined with a conforming chromium deposit. After thirty (30) minutes. there was, of course, a heavier chromium deposit, and in addition to complete coverage of the entire body of the drill, the edges 12 and 34 were still sharply defined so that upon subsequent drilling with 'the tool, it performed excellently. It wasnt until a specimen had been in the tank one hundred and fifty (150) minutes that marks of the mesh-fabric began to show on the land portion of the drill; but still there was no treeing" on the edges 12 and 34.

Thus it is apparent that the readily deformable wiremesh fabric acts to distribute the current in a fashion which permits over-all metal coverage of an object having a multiplanar area. The object itself may serve as a support for the current distributing means. Recesses,

H as well as projections, can be deposited with metal from baths having poor throwing power, While avoiding treeing or undue rounding on the sharp edges or projections. The part of the wire-mesh fabric overlying a projection and recess may be in contact with the projection or spaced therefrom, and the spacing is not critical insofar as avoidance of treeing is concerned. Heavy deposits may be obtained without sacrificing conformity to the contour of the underlying object. The sharpness of a cutting edge may be retained with all the advantages of having the edge covered with chromium; namely, low coeflicient of friction, resistance to spalling, resistance to corrosion, and extreme hardness.

Figs. 6 and 7 illustrate the invention as applied to a cross-cut saw C. For this application, the Wire-mesh fabric B is shaped around the cutting teeth 36 and is of a width to extend for a short distance beyond and down on the body of the saw. The mesh-fabric strip is cut to a length to extend around the lateral non-cutting edges 38 and 40 so that, Without any additional support, the saw serves as a support for the current distributing means. Care is exercised not to push the teeth through the wire fabric. For this application, a hooked strap 42 may be passed through one of the apertures 44, which ordinarily serves as a means for securing a handle to the saw. When hung from the cathode bar of the chromium plating tank, and with the wire-mesh covered side facing an anode in an industrial chromium plating bath, which may be of the type described above, the teeth are plated so that they maintain their sharpness and do not require sharpening. The chromium deposit follows the multiplanar area presented by the saw teeth without treeing or undue rounding.

Fig. 8 illustrates the invention as applied to a spur gear D, for which application the wire-mesh fabric B is conformed around the extreme outer periphery to cover the teeth 46, and the intermediate recesses 48. The strip B is cut to width so that it extends down on the body of the gear, below the base of the recesses. The seam formed by the abutting edge on the periphery is located between a pair of teeth. In plating a gear, the strap or means for connecting the gear to the cathode bar may be passed through its bore 50, and suspended in a bath surrounded by a plurality of anodes equi-distantly spaced from its periphery or teeth.

While the chromium plating of several specific objects having multi-planar areas has been described, it will, of course, be understood that the invention is applicable to a wide Variety of irregularly shaped objects. The deformable, porous, electrically-conductive fabric or sheet has practically universal application in the sense that it can be used to cover the multi-planar area of practically any object, and with or without auxiliary holding means, may be supported upon the object itself.

While the invention has been specifically described with regard to chromium plating, it will be understood that any plating solution having poor throwing power, or requiring relatively high current densities, may be used. For example, the type of objects under consideration may be plated from a copper cyanide bath.

The term porous, electrically-conductive fabric as used in the claims is intended to include woven wiremesh fabric or a foraminous metal sheet formed by perforating or punching a continuous sheet.

It is believed that the novel method and apparatus of the present invention, as well as the advantages thereof. will be apparent from the foregoing detailed description. It will also be apparent that while the invention has been shown and described in several preferred forms, changes may be made in the method and structure disclosed without departing from the scope of the invetnion, as sought to be defined in the following claims.

I claim:

1. A method of electrodepositing metal from a bath having poor throwing power onto an electrically-conductive object having a multi-planar area comprising-covering the multi-planar area with a porous, electricallyconductive fabric, making the fabric-covered object the cathode in the bath, passing current between the object and an anode, and separating the fabric from the plated object.

2. A method of electrodepositing metal from a bath having poor throwing power onto an electrically-conduc tive object having a multi-planar area comprising making the object the support for a porous, electrically-conductive fabric with the fabric overlying the multi-planar area, making the fabric-covered object the cathode in the bath, passing current between the object and an anode, and separating the fabric from the plated object.

3. A method of electrodepositing metal from a bath having poor throwing power onto an electrically-conductive object having a multi-planar area comprising placing a deformable, porous, electrically-conductive fabric upon the object so that the fabric overlies the multiplanar area, bending the fabric about the object so that the object serves as a support for the fabric, making the fabric-covered object the cathode in the bath, passing current between the object and an anode, and removing the fabric from the plated object.

4. A method of electrodepositing chromium onto an electrically-conductive object having a multi-planar area comprising covering the multi-planar area with a porous, electrically-conductive fabric, making the fabric-covered object the cathode in a chromium plating bath, passing current between the object and an anode, and separating the fabric from the plated object.

5. A method of electrodepositing chromium onto an electrically-conductive object having a multi-planar area comprising making the object the support for a porous, electrically-conductive fabric with the fabric overlying the multi-planar area, making the fabric-covered object the cathode in a chromium plating bath, passing current between the object and an anode, and separating the fabric from the plated object.

6. A method of electrodepositing chromium onto an electrically-conductive object having a multi-planar area comprising placing a deformable, porous, electricallyconductive fabric upon the object so that the fabric overlies the multi-planar area, bending the fabric about the object so that the object serves as a support for the fabric, making the fabric-covered object the cathode in a chromium plating bath, passing current between the object and an anode, and removing the fabric from the plated object.

7. A method of electrodepositing chromium onto the cutting edge of an electrically-conductive tool comprising making the tool the support for a porous, electricallyconductive fabric with the fabric overlying the cutting edge, making the tool the cathode in a chromium plating bath, passing current between the tool and an anode, and separating the fabric from the plated tool.

8. A method of electrodepositing chromium onto the cutting edge of an electrically-conductive tool comprising placing a deformable, porous, electrically-conductive fabric upon the tool so that the fabric overlies the cutting edge, bending the fabric about the tool so that the tool serves as a support for the fabric, making the fabriccovered tool the cathode in a chromium plating bath, passing current between the tool and an anode, and removing the fabric from the plated tool.

9. A method of electrodepositing chromium onto an electrically-conductive drill comprising placing a deformable, porous, electrically-conductive fabric upon the drill so that the fabric overlies the cutting edges, land and flutes, bending the fabric about the drill so that the drill serves as a support for the fabric, making the fabriccovered drill the cathode in a chromium plating bath, passing current between the drill and an anode, and re moving the fabric from the plated drill.

10. A method of electrodepositing chromium onto an 6 electrically-conductive saw comprising placing a deformiable, porous, electrically-conductive fabric upon the saw so that the fabric overlies the teeth of the saw, bending the fabric about the saw so that the saw serves as a support for the fabric, making the fabric-covered saw the cathode in a chromium plating bath, passing current between the saw and an anode, and removing the fabric from the plated saw.

11. A method of electrodepositing chromium onto an electrically-conductive gear comprising placing a deformable, porous, electrically-conductive fabric upon the gear so that the fabric overlies the gear teeth and adjoining recesses, bending the fabric about the gear so that the gear serves as a support for the fabric, making the fabric-covered gear the cathode in a chromium plating bath, passing current between the gear and an anode, and removing the fabric'from the plated gear.

12. A method of electrodepositing metal from a bath having poor throwing power onto an irregularly shaped, electrically-conductive object having a projection and a recess comprising covering the object including the projection and recess with a flexible, readily deformable, porous, electrically-conductive fabric so that the fabric is in contact with the projection, making the fabriccovered object the cathode in the bath, passing current between the object and an anode, and separating the fabric from the plated object.

13. .A method of electrodepositing metal from a bath having poor throwing power onto an irregularly shaped, electrically-conductive object having a projection and a recess comprising making the object the support for a porous, electrically-conductive fabric, with the fabric overlying the projection and recess and in contact with the projection, making the fabric-covered object the cathode in the bath, passing current between the object and an anode, and separating the fabric from the plated object.

14. A method of electrodepositing metal from a bath having poor throwing power onto an irregularly shaped, electrically-conductive object having a projection and a recess comprising placing a deformable, porous, electrically-conductive fabric upon the object so that the fabric overlies the projection and recess, bending the fabric about the object so that the object serves as a support for the fabric and the fabric is in contact with the projection, making the fabric-covered object the cathode in the bath, passing current between the object and an anode, and removing the fabric from the plated object.

15. A method of electrodepositing metal from a bath having poor throwing power onto an irregularly shaped, electrically-conductive object having a projection and a recess comprising covering the object including the projection and recess with a flexible, readily deformable, porous, electrically-conductive fabric so that the fabric is spaced from the projection, making the fabric-covered object the cathode in the bath, passing current between the object and an anode, and separating the fabric from the plated object.

16. A method of electrodepositing metal from a bath having poor throwing power onto an irregularly shaped, electrically-conductive object having a projection and a recess comprising making the object the support for a porous, electrically-conductive fabric, with the fabric overlying the projection and recess and spaced from the projection, making the fabric-covered object the cathode in the bath, passing current between the object and an anode, and separating the fabric from the plated object.

17. A method of electrodepositing metal from a bath having poor throwing power onto an irregularly shaped, electrically-conductive object having a projection and a recess comprising placing a deformable, porous, electrically-conductive fabric upon the object so that the fabric overlies the projection and recess, bending the fabric about the object so that the object serves as a support for the fabric and the fabric is spaced from the projection, making the fabric-covered object the cathode in the bath, passing cun'ent between the objectand an anode, and removing the fabric fromthe' plated object.

18. A method of electrodepositing chromium onto an irregularly-shaped, electrically-conductive object having a projection and adjoining recess comprising wrapping a deformable, porous, electrically-conductive fabric upon the object so that the fabric overlies the projection and recess and is supported by the object, said fabric having an approximately one-sixteenth inch mesh size, placing the fabric-covered object as the cathode in a chromium plating bath, the connection with the source of current being made with the object, passing current between the object and an anode to plate the object, removing the fabric-covered object from the bath, and removing the fabric from the plated object.

References Citedin the file of this patent UNITED STATES PATENTS 1,567,791 Duhme Dec. 29, 1925 1,868,052 Dubpernell July 19, 1932 2,194,551 Holman Mar. 26, 1940 2,434,417 Kugler Jan. 13, 1948 2,745,798 Haueisen et a1. May 15, 1956 FOREIGN PATENTS 4%,113 GreatBritain Nov. 23, 1939 

1. A METHOD OF ELECTRODEPOSITING METAL FROM A BATH HAVING POOR THROWING POWER UNTO AN ELECTRICALLY-CONDUCTIVE OBJECT HAVING A MULTI-PLANAR AREA COMPRISING COVERING THE MULTI-PLANAR AREA WITH A POROUS, ELECTRICALLYCONDUCTIVE FABRIC, MAKING THE FABRIC-COVERED OBJECT THE CATHODE IN THE BATH, PASSING CURRENT BETWEEN THE OBJECT AND AN ANODE, AND SEPARATING THE FABRIC FROM THE PLATED OBJECT. 